Labial bow

Question 1

What is a labial bow?

Answer 1

A largely horizontal wire labial to the incisor teeth

Question 2

What are the uses of a labial bow?

Answer 2

Retention: holding the appliance up anteriorly

Guidance: of canines during retraction

Active: retracting of the incisors

Retention: holding the corrected teeth in their new position

Question 3

What are the 4 elements of a removable appliance?

Answer 3

Active components

Retentive components

Baseplate

Anchorage

Question 4

Which of the 4 elements of a removable appliance does a labial bow fulfil?

Answer 4

2 = active and retentive component

Question 5

What are the different orthodontics active components?

Answer 5

Springs, bow and screws

Question 6

What are the two types of labial bow?

Answer 6

High labial bow and reverse looped bow

Question 7

What is a high labial bow suited for?

Answer 7

An active component only (made of very thin wire and contains apron spring)

Question 8

What is a reverse looped bow suited for?

Answer 8

More versatile (active and retentive)

Question 9

In a reverse looped bow where is the loop situated?

Answer 9

Beyond the working area

Question 10

What is retention?

Answer 10

The capacity of an appliance to remain fixed in the mouth

Question 11

E.g. of labial bow positions relative to the normally angulated central incisor…

Answer 11

High gingival position may engage some undercut but incisor has little undercut -> the bow is too flexible and the undercut too little to provide good retention

• should be at bottom of incisal 1/3 (correspond roughly with where the baseplate is on the opposite side)
• n.b. wire slides down the tooth as they straighten during treatment

Question 12

How do we tighten the labial bow?

Answer 12

By squeezing the loop = lift it back up = flattens the top of the bow

Question 13

How do we raise or lower the bar?

Answer 13

By adjusting the flat bit of the loop = Flexes the bow so it sits at the right position

Question 14

Name two alternative anterior retainers?

Answer 14

Southend clasp (anterior retainer of choice)

Adams anterior clasp

Question 15

What is a Southend clasp?

Answer 15

Fits right down to the gingival margin = stiff and engages a lot of undercut

Question 16

What does an Adams anterior clasp look like?

Answer 16

Question 17

How does a labial bow control tooth movement?

Answer 17

It can guide canine retraction (by preventing the canine escaping labially and lessen any tendency to rotate)

Question 18

How does a labial bow move teeth?

Answer 18

1. Teeth move at right angles to point of contact of the spring (n.b. not necessarily in the same direction as the spring moves as it goes passive)
2. where the line of force does not pass through the centre of resistance the tooth will rotate (see pic)

Question 19

How may a labial bow help in treatment of Class II div I (lower jaw appears further back and teeth proclined = over-jet)?

Answer 19

1. Retract upper canines and reduce overbite
2. Retract proclined incisors

Question 20

Which thickness of wire should be used to make a labial bow for retention?

Answer 20

Stiff (thick) wire

Question 21

Which thickness of wire should be used to make a labial bow for guiding a canine?

Answer 21

Stiff (thick) wire

Question 22

Which thickness of wire should be used to make a labial bow for retracting incisors?

Answer 22

Flexible wire

Question 23

Which thickness of wire should be used to make a labial bow for retaining tooth positions?

Answer 23

Stiff (thick) wire

Question 24

The difficulty with needing a flexible wire for retracting incisors following retraction of canines in Class II div I?

Answer 24

Once canines have been moved into the wanted position by the spring we split the bow to make it much more flexible while retracting the incisors (curl the ends a little) -> to get the right force and good range of action = needs to activate 3 mm = tighten curve of bow in area where canines used to be

Bow can be made much stiffer again by soldering the ends together

n.b. not frequent method any more but works well in the right case

Question 25

How far past the 5 does the labial bow extend?

Answer 25

3/4 of the way past the 5

Question 26

What faults can occur in labial bow construction?

Answer 26

• Flyover not high enough
• kinked labial bow

Question 27

Why is the flyover not high enough an issue?

Answer 27

Means the canine cannot be fully retracted because wire is in the way